Centrifuge having a sealed housing



1956 L. SHAPIRO 3,269,647

CENTRIFUGE HAVING A SEALED HOUSING Filed Nov. 18, 1963 2 Sheets-Sheet l INVENTOR. 22

LEONARD SHAPIRO ATTORNEY Aug. 30, 1966 SHAPIRO CENTRIFUGE HAVING A SEALED HOU SING 2 Sheets-Sheet 2 Filed Nov. 18, 1963 M zzi miwin INVENTOR.

LEONARD SHAPIRO ATTORNFY United States Patent 3,269,647 CENTRIFUGE HAVING A SEALED HOUSING Leonard Shapiro, Upper Darby, Pa., assignor to Pennsalt Chemicals Corporation, a corporation of Pennsylvania Filed Nov. 18, 1963, Ser. No. 324,545 9 Claims. (Cl. 2331) This invention relates to centrifuges. More specifically this invention relates to centrifuges with enclosures to make possible operation in isolated atmospheres such as under pressures above or below that of the ambient pressure, or in an atmosphere of a gas other than air. Still more specifically this invention relates to centrifuges With such enclosures and providing seal means between the enclosure and the centrifuge drive means.

There is need for such equipment in many processes. Pressure conditions are maintained, for instance, in the centrifugal separation of the desirable insoluble form of polypropylene from theundesirable soluble form of the polymer in hexane solution. This operation is preferably carried out at temperatures above the atmospheric boiling point of hexane. In other cases it may be desirable to operate below the boiling point of the solvent in a pressurized nitrogen atmosphere to preclude invasion of air which could support an explosion.

In the separation of water and solids from a highly viscous tar-like material it is often necessary to heat the mixture to very high temperatures to reduce viscosity and permit pumping and centrifugation. In such a process the centrifuge must be held under pressure, for at atmospheric pressures the temperatures would cause the water to vaporize leaving an unworkable mixture.

Similarly, in the treatment of inorganics, special atmospheres are necessary or desirable. The centrifugal removal of sludge in the processing of titanium trichloride, for instance, must be accomplished at process line pressures to prevent the reaction of the process stream and air with a consequent escape of hydrogen chloride and decomposition of the product upon contact by water vapor.

A less exotic, but equally important, need for processing in an isolated atmosphere may be found in the production of ordinary fruit juices. To avoid flavor degradation of orange juice, for instance, it is important that the centrifugal separation of the solids from the liquids be accomplished in a non-oxidizing atmosphere. For this purpose it is desirable to accomplish a centrifuging step in an atmosphere of some relatively inert gas such as nitrogen.

One of the problems inherent in the development of a centrifuge adapted for isolated atmospheric conditions is the design of sealing means permitting penetration of the centrifuge drive shaft into the pressure tight centrifuge casing. The problem arises as a consequence of (l) the considerable pressure differential between the interior and the exterior of the casing and (2) the necessity for freedom of movement of the centrifuge drive shaft in lateral directions as the rotating parts pass through critical speeds or undergo lateral aberrations in the course of normal operation. In addition, especially noticeable in suspended centrifuge mountings, are movements of the shaft in axial directions due to pressure changes within the casing acting on the various resilient mounts.

Early attempts to meet this problem have involved the use of a mechanical seal required to accommodate both lateral and axial movements. Such arrangements have not been satisfactory, primarily because spring pressed 3,269,647 Patented August 30, 1966 seals accommodating lateral movement have been subject to leakage due in part to surface irregularities and have been susceptible to accidental damage, are prohibitively expensive, require cleaning and frequent inspection.

According to the present invention seal'is made by elast-omeric material mounted to accommodate lateral movement of the drive shaft hy movement under shear. In the preferred embodiments the elastomer is in the form of alternate laminae of rigid material such as metal and elastomeric material to withstand high pressure differential. Coupled with such an arrangement accommodation of axial movement of the drive shaft is made possible by sliding mechanical seal means which greatly simplify the pressure-tight connection between the drive shaft mounting and the casing. The connection may be automatically made by simply bringing together the parts to be sealed.

An object of the invention, therefore, is to provide a pressure-tight connection between the drive shaft mounting and the pressure-tight casing of a centrifuge.

A further object of the invention is to provide for such a connection simple means for its association with the casing.

Other features and objects of the invention will become apparent to those skilled in the art upon review of the following specification illustrating embodiments of the invention and including the drawings wherein:

FIGURE 1 is a fragmentary elevational view, partly in section, of a centrifuge embodying the invention;

FIGURE 2 is an enlargement of the seal portion of FIGURE 1; and

FIGURES 3, 4 and 5 are comparable sectional views of modification of the seal arrangement under the invention.

Referring more specifically to the drawings, a centrifuge embodying the invention is shown in FIGURE 1 and generally designated 10. It comprises a centrifuge bearing assembly 12 with depending drive shaft 14 and the centrifuge =bowl 16. Surrounding the howl and enclosing it from the ambient atmosphere is the pressure-tight casing 18 which may comprise two mating casing portions 20 and 22 secured together and clamping between them a support ring 24 which is securely held up in the centrifuge frame, not shown. Secured within the upper casing portion 20 is an annular baflle 26 extending inwardly to collect material discharged over the Weir 28 of the centrifuge bowl. Spaced above the baflle 26 is a second baflie 30 also secured to the upper casing portion 20 and extended inwardly to collect efiluent from the extension 32. The lower casing portion 22 (only a small portion of which is shown) serves to collect heavy discharge from the centrifuge nozzles 34. Appropriate conduits (not shown) are connected to each of the collectors to lead off the discharges respectively.

Feed to the centrifuge shown is delivered to the lower end of the centrifuge bowl by -a feed tube which penetrates casing portion 22. The feed tube is stationary and delivers its charge to a pocket in the lower end of the centrifuge. This arrangement is not shown, but is conventional, as, for instance, in the Ayres Patent 2,138,467 issued November 29, 1938.

Referring more specifically to the bearing assembly 12, the centrifuge support plate 36 as shown is resiliently mounted on the centrifuge frame 37 in such a way that some vertical movement is possible. The plate presents an upstanding hollow boss 38 mounting sets of bearings 40, the inner races of which engage the spindle 42 and are held against vertical displacement with respect to the housing by the nut 44 and spacer 46. The outer races of the bearing sets are held up in the boss by the support ring 48 secured to the support 36.

Lubrication for the bearings is provided through appropriate channels 50 in the support and boss and is collected from an opening 52 in the ring 48 in a suitable annular pan 54.

The spindle carries a sealing ring 56, and the lower end of the support ring 48 has secured to it an annular seal mount 58 thereabout. The support ring and the seal mount 58 each carry commercially available springpressed seal units 60 having faces which bear against the sealing ring 56. Since there is no relative lateral movement between the spindle 42 and sea-l mount 58 the sealing problem can be easily met by such units. As shown in FIGURE 1, the spindle is hollow and the opening in its lower end is tapered to complement the upper end of the drive shaft 14. The upper end of the drive shaft is hollow and internally threaded and receives the lower threaded end of the draw bar 62. At its upper end (not shown) the draw bar is formed with an enlarged head which engages the upper end of the pulley 64. As shown the pulley 64 is united in radial movement with the spindle housing by the key 66.

In operation a drive belt engages the pulley 64 to rotate the centrifuge at a suitable speed.

Focusing now on the area of the invention, the seal mount 58 carries on its lower end a collar element 68 sealed against the underside thereof. The collar element 68 is provided at its outer perimeter with a downward guard flange.

Confronting the collar element 68 surrounding the drive shaft 14, and secured in an opening in the top of the casing portion 20 is the collar element 70. The upper 'end of the collar element 70 preferably extends above the downward lip of the guard flange on the collar element 68. Secured to the lower end of the collar element 70 is an inwardly extending annular plate having a downward tubular extension, the plate and extension comprising a splash guard 72 to protect the seal from the liquid discharging from extension 32.

In the embodiment shown in FIGURE 1 the collar element 68 has secured to it the upper end of a composite resilient tubular sealing conduit 74. The joint between the conduit and the element may be made by a suitable adhesive or by for instance mechanical means penetrating down into the conduit a short distance insufficient to affect the lateral flexing of the conduit. The lower end of the conduit is secured in a similar fashion to a sealing ring 76 which preferably extends outwardly and upwardly and engages the inner surface of the collar element 70 in a sliding fit. Suitable O-rings may be provided in the sealing ring 76 as shown.

Referring to the enlargement (FIGURE 2) the composite lateral resilient tubular sealing conduit 74 preferably comprises alternate laminae of an elastomer 74a and a rigid material 74b such as metal. In a preferred embodiment now in service the elastomer is a silicone rubber especially well adapted for operation at low temperatures, for instance, 40 F. or high temperature, +350 F. The height of the rubber laminae is .005". The rigid laminae are stainless steel and are .003" high. The laminae are Ms" thick. In all the preferred embodiments of the invention, the height of the elastomeric laminae are significantly less than their thickness to assure proper transfer of stress to the rigid lamina. The laminae are joined by an epoxy and under actual operating conditions have been found to withstand pressures in excess of 50 p.s.i.

In an alternate form the elastomer is a buna-N rubber which has been found exceptionally resistant to chemical erosion and is suitable for many uses. The silicone rubber embodiments are preferred at low temperatures, however, since the buna-N rubber exhibits a tendency to stiffen and lose its ability to accommodate lateral movement.

As shown in FIGURE 2 the outer lower corner of the sealing ring 76 is formed with a large chamfer 76a. Similarly the inner upper corner of the ring element 70 is formed with chamfer 7051. This is of valuable assistance in the uniting of the bearing assembly and the casing, for in a preferred embodiment the bearing assembly and drive are raised vertically above the centrifuge bowl to disassemble the unit. When the bearing assembly is returned to its operating position the chamfers 76d and 70a guide the sealing ring 76 into proper relation with the collar element 70. v

The modification shown in FIGURE 3 is in operation very similar to the preferred embodiment of FIGURES 1 and 2. In the FIGURE 3 embodiment the casing portion 20 presents an upstanding annular flange 80 disposed about the drive shaft opening. The collar element 82 secured to the upper end of the annular flange 80 projects inward and has secured to an under surface the upper end of the lateral resilient tubular sealing conduit 84. In the embodiment shown the conduit 84 is comparable in structure to the conduit 74 of the FIGURES 1, 2 embodiment. To the lower end of the conduit 84 is secured the sealing ring 86 which has inwardly and upwardly extending flange slidingly engaging the outer surface of the collar element 88. The collar element 88 may be secured to or integral with the seal mount, such as 58 of the FIGURE 1 embodiment.

Mounted on the annular flange 80 is an inward and downwardly extending splash guard 90 comparable to the guard 72 of the FIGURES 1, 2 embodiment.

Referring now to the FIGURE 4 modification the hemisphere 20" has secured about the drive shaft open ing the annular flange to the upper end of which is secured the collar element 102. An undersurface of the collar element 102 mounts the laterally resilient tubular sealing conduit 104. The lower end of the conduit 104 mounts the sealing ring 106 which slidingly engages a surface on the collar element 108 which maybe secured to or be integral with the seal mount, such as 58 of the FIGURE 1 embodiment.

In the FIGURE 4 embodiment the conduit 104 as illustrated may be of laminae of larger dimension than in the FIGURES 2 and 3 embodiments. For instance, in one machine embodying the structure shown'in FIG- URE 4 the elastomer elements are Mr" thick and are between the inner and outer periphery. They are made of silicone rubber. The rigid laminae are of stainless steel and are thick and the same distance between the inner and outer periphery.

The FIGURE 5 embodiment is comparable to that of FIGURE 3 and primed reference numerals are used to designate corresponding parts. The inward collar element secured to the seal mount 88 places the sliding surfaces of the references 86' and element 120 at the smallest radius possible. This reduces to a minimum the force due to pressure acting upward on the bearing assembly and downward on the centrifuge bowl.

By virtue of the laminated structure of the preferred embodiments of the invention the desired degree of accommodation to lateral movement is possible without any wear problems as might be with the conventional woven hose. At the same time the use of thin layers of elastomer permit the sealing conduit to withstand considerable pressure, pressures which a conduit of comparable dimension made entirely of elastomer without the rigid laminae could not withstand. The thin laminae of elastomer can withstand the pressures by deforming and transferring their stress to the adjacent rigid members. Hence the pressures which the conduit is able to withstand are the pressures which the rigid laminae are abl to withstand.

This stress is well in excess of the allowable stress for an elastomer.

On the other hand adapting the formula to the 1amh= the height of the elastomeric lamina (assuming they are uniform) h'=the height of the rigid lamina (assuming they are uniform).

then

where -4000 p.s.i.

The rigid laminae which carry the full load can easily withstand this load. And still the conduit has the required degree of flexibility.

Reference once more to the FIGURES 3, 4 and 5 embodiments show comparable chamfering of the collar elements and engaging sealing rings to facilitate the guiding of the two together as the driving assembly is lowered to the casing in the preferred embodiment.

Those skilled in the art will be able to recognize from a review of the above disclosure that the invention provides sealing means between the drive and casing of a pressure-tight centrifuge which permits easy lateral movement of the centrifuge and its shaft and at the same time is able to withstand high operating pressures without failure. As an additional benefit in the embodiments shown the union of the bearing assembly and the casing is greatly facilitated by the arrangement disclosed.

It should be understood that variations are possible within the scope of the invention. Therefore, having particularly described my invention, it is to be understood that this is by way of illustration, and that changes, omissions, additions, substitutions, and/ or other modifications may be made without departing from the spirit of the invention. Accordingly, it is intended that the patent shall cover, by suitable expression in the claims, the various features of patentable novelty that reside in the invention.

I claim:

1. A centrifuge for separating components of feed mixture in an isolated atmosphere and comprising a centrifuge bowl and a centrifuge drive means spaced from each other but operatively connected by a drive shaft, a pressure-tight casing enclosing the centrifuge bowl, the casing being provided with an opening receiving the drive shaft, a first collar element surrounding the opening and secured to the casing, the drive shaft being supported externally of the casing by support means, a second collar element surrounding the shaft and secured to the support means in pressure-tight relation to the shaft, a laterally resilient tubular sealing conduit surrounding the shaft and secured at one end to one of the collar elements, the other end carrying a sealing ring sealingly engaging in sliding fit the other collar element on a surface parallel to the axis of the shaft, the conduit comprising generally radial laminae including at least two laminae of elastomer and one of rigid material, the rigid lamina being disposed intermediate the elastomer laminae, contiguous faces of the laminae being bonded together to prevent relative movement thereof.

2. A centrifuge as described in claim 1 wherein in axial cross-section the dimension of the elastomer lamina in the direction parallel to the axis is substantially less than the dimension of the elastomer element in the direction along a radial line.

3. A centrifuge as described in claim 1 wherein the sealing ring and the collar element it engages are chamfered, on the edges respectively most remote from the support means and casing to which said sealing ring and the said collar element are respectively attached, where by the act of connecting the units is facilitated.

4. A centrifuge as described in claim 1 wherein the first collar element mounts a depending splash guard.

5. A centrifuge as described in claim 1 wherein an O-ring is disposed in one of the engaging surfaces of the sealing ring and the said collar element.

6. A centrifuge as described in claim 1 wherein the dimension of the elastomer lamina in the direction axial of the shaft is on the order of .005 inch and the dimension of the rigid lamina in the same direction is on the order of .003 inch.

7. A centrifuge as described in claim 1 wherein the dimension of the elastomer lamina in the direction axial of the shaft is on the order of .005 inch and the dimension of the elastomer lamina in the radial direction of the shaft is A; inch.

8. A centrifuge as described in claim 1 wherein the radius to the inside wall of the conduit is less than the radius to the engaging surfaces of the sealing ring and the engaging collar element.

9. For a centrifuge having a support means, a centrifuge bowl surrounded by a pressure-tight casing and a drive shaft mounted in the support means and supporting the bowl, the drive shaft penetrating the casing through an opening intermediate the bowl and the support means, a seal assembly comprising: -a pair of collar elements mounted on the casing about the opening and on the support means about the shaft in pressure-tight relation therewith, respectively, a laterally resilient tubular sealing conduit surrounding the shaft and secured at one end to one of the collar elements, the other end carrying a sealing ring sealingly engaging in sliding fit the other collar element on a surface parallel to the axis of the shaft, the conduit comprising radial laminae including at least two laminae of elastomer and one of rigid material, the latter lamina being disposed intermediate the elastomer laminae, contiguous faces of the laminae being bonded together to prevent relative movement thereof.

References Cited by the Examiner UNITED STATES PATENTS 3,073,517 171963 Pickels et al. 233-32 3,173,696 3/1965 Reinhardt et al. 277 -53 3,194,492 7/1965 Koflinke er al. 277 3 X FOREIGN PATENTS 22,529 6/1948 Finland.

M. CARY NELSON, Primary Examiner.

HENRY T. KLINKSIEK, Examiner. 

1. A CENTRIFUGE FOR SEPARATING COMPONENTS OF FEED MIXTURE IN AN ISOLATED ATMOSPHERE AND COMPRISING A CENTRIFUGE BOWL AND A CENTRIFUGE DRIVE MEANS SPACED FROM EACH OTHER BUT OPERATIVELY CONNECTED BY A DRIVE SHAFT, A PRESSURE-TIGHT CASING ENCLOSING THE CENTRIFUGE BOWL, THE CASING BEING PROVIDED WITH AN OPENING RECEIVING THE DRIVE SHAFT, A FRIST COLLAR ELEMENT SURROUNDING THE OPENING AND SECURED TO THE CASING, THE DRIVE SHAFT BEING SUPPORTED EXTERNALLY OF THE CASING THE SUPPORT MEANS, A SECOND COLLAR ELEMENT SURROUNDING THE SHAFT AND SECURED TO THE SUPPORT MEANS IN PRESSURE-TIGHT RELATION TO THE SHAFT, A LATERALLY RESILIENT TUBULAR SEALING CONDUIT SURROUNDING THE SHAFT AND SECURED AT ONE END TO ONE OF THE COLLAR ELEMENTS, THE OTHER END CARRYING A SEALING RING SEALINGLY ENGAGING IN SLIDING FIT THE OTHER COLLAR ELEMENT ON A SURFACE PARALLEL TO THE AXIS OF THE SHAFT, THE CONDUIT COMPRISING GENEALLY RADIAL LAMINAE INCLUDING AT LEAST TWO LAMINAE OF ELASTOMER AND ON OF RIGID MATERIAL, THE RIGID LAMINA BEING DISPOSED INTERMEDIATE THE ELASTOMER LAMINAE, CONTIGUOUS FACES OF THE LAMINAE BEING BONDED TOGETHER TO PREVENT RELATIVE MOVEMENT THEREOF. 